[sdiy] 555 vco success

[Scott Gravenhorst]

Jim Patchell <patchell at silcom.com> wrote:
>
>
>Scott Gravenhorst wrote:
>
>> Excellent!  When something you made works, it's a total
>> thrill, is it not?  Now you can play with it!
>>
>> Interesting that they don't soft synch.  I 'measure'
>> how close together the VCOs are tuned before synching
>> by getting them  as close as possible and then timing
>> how long it takes the phasing sound to repeat.  Someone
>> correct me if this is wrong, but if that phasing sound
>> takes one second to complete, the oscillators are
>> detuned by 1 Hertz.  If it takes 5 seconds, then they
>> are at 0.2 Hz apart (1/5 Hz), etc. This is how I determine
>> what resistance to soft synch the circuit has.  The smaller
>> the number of Hz, the better.
>>
>
>    This is what I do.  For the VCO's I did, I found that 10 seconds was about
>the limit.  This was due to the fact that the frequency stability beyound this
>point made it difficult to do a measurement.  I figured if they don't softsync at
>..1hz difference, it may not make any difference anyway.

Probably because it will actually do longer cycles if it 
will do 1Hz.  Both of my FatMan synths have a coarse and
fine pitch control, so it's easy to trim them out until
they almost lock.  I've gotten cycles times between 12
and 15 seconds with modified FatMan VCOs.  It's kinda
cool to listen to with filter freq and rez maxed.  They
won't do that stock.

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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